Tetrahydrothiophenes



Patented pr. 4, 1950 n 4 laiins (C1. 26o-329) o o o'Rf found 'that vthere -is'M-so'me' advantage in usingy two" 0 51. mole'sof'sodiumalkoxide per mole'of ester to bef l H cs'clized.'y Nevertheless, `goodresults are oltained.1 withonly one ngolefofcondensingagent perm'ole Hail? JH-mHn-R orestf'er. Condexising 'agent'sgothertharithe aI`.-

kaiirrnetar aikoxides, Whionmay oeVusoofor"the;` geraete s; 1 the Values 1 to 8 inclusive, wherein the aliphatic metal .amldes .(Suc-h as soqa'm1,d)..?nd 91.53995 l metalhc combmations such as trlphenylmethylcarbon cham, -CH2n-, may be either straight sodm. and:meswmggum bmdl or branched; and R is a radic'aI'of" the class ,A COOR' al. 10X aralkoxv andz lkoxy, The im 15A Although we prefer to employ dry benzene as `y y" y" a a solventl in the ratio of about 2 liters of bezi'ef' glgogesgoggsses methods`for obtalmng per mole of ester when conducting thisfcyclza'#t tion, other so1vents-may be usedfinehiding dry? Tlesoo'rnoondsof the-inventionar'usefurfr" the preparationof'.compsitionspossssing valulhel tofcflr lutgxatenvls able@ therapeutic prODertieS; They arf'illtw' 20* liqzid rllay be used as a reaction medium or sollflilyiusefllasntrmdats fofthfsyn'thesis'ff vent The presence of 'a relativen7 large volume gonlis gisstymg bmtm actwlty and posslbly of solvent generally "Lfavors the intramolecular According to this invention 4-carboalky1oxycbycnzatio' O-thtthr hanthe eaction may 25 e carrie ou `Wi ou a i uent y using an 3-keto-2-a1ky1-tetrahydrothiophenes of the above alkali Aalkoxide as the condensing agent and by type are obtained by an internal condensatonl' it f. within a -carboalkoxyalkyl-a-carboalkoxyalkyl llmlcige acohol as mpldly as '1t 1s formed m sulfide' Wherem the alkyl carrymg the 'ca-rbo' Thefcyclizationgenerally goes to completion# givenf The condensing agent" may be 'ROM',`

:3 times with benzene.

.Na2SO4.

'tracted with benzene. y (extract with water, it is removed through a colY solution of 38.8 g. (0.1115 mole) of -c'aibethxyethyl d, o-dicarbethoxyamyl sulde in 50 ml. of dry benzene is added in two portions. The mixture is shaken and cooled when it becomes warm. The sodium ethoxide goes into solution very readily but after several minutes the sodium derivative of the keto ester separates. The mixture is allowed to stand overnight.

The cooled mixture is acidied with a solution of 20 m1. of glacial acetic acid in 160 ml. of water.

Layers are separated and the benzene layer is extracted twice with sodium bicarbonate solution,

is washed with saturated sodium chloride solution and dried over sodium sulfate.. is removed leaving a light brown oil which gives a cherry-red ferrie chloride test and forms a green copper salt when shaken with copper acetate solution.

The keto ester is purified through the copper salt which weighs 33.3 g. vA recrystallized sample melts at 11S-119.

6.63; Cu, 9.51. Found: C, 50.76; H, 6.56; Cu, 9.70.

The keto ester is regenerated by shaking an ether solution of the copper salt with sulfuric acid. The ether layer is washed with sodium bi'- carbonate solution and dried over sodium sulfate Ether and salt are removed leaving 30 g. of keto" ester as a dark red oil which-lightens to a yellow color on long standing; yield 89%.

Found: C, 55.53; H, '7.36.A l

Its formula and its production from the starting material may be represented as follows:

COOCxHs H; COOCaHs VThe alcohol from a solution of 30.5 g. (1.328 moles) of sodium in 590 ml. of absolute alcohol is removed at reduced pressure until the NaOEt is completely dry (160-200 C. at 23 mm. for two hours). The NaOEt is suspended in dry benzene (900 ml.) and treated with 235 g. (0.664 'molelof carbethoxyethyl-a-carbethdxy-d-phenoxybutyl sulde in 300 ml. of dry benzene. After4 shaking thoroughly the solution is allowed to standoverfv.

night. The cooled solution is acidified with 147 ml. of glacial acetic acid in 1200 ml. of water. jBenzene layer is separated. Water layer istreate Benzene v v ed with 5 ml. of concentrated HC1l andextractefCv'ir The extracts and benzene .layer are washed three times vwith bicarbonate solution, twice with water and clarified with Benzene is removed through column lleaving a residue of 180 g. A similar run is made'4 using 190 g. of ester.l The residue in this case :amounts to 155 g. The bicarbonate extracts from both runs are acided and combined, then eX- After washing benzene umn leaving a residue of about 33 g. This. residue gives a. FeCla test, green turning toblue then la solution of 56 ml. of HzSO'4 in 1000 ml. of H2O vand'covered with 1 l. of ether. The ether layer is separated. The water layer is extracted twice twith ether, combined' ether layers are washed fwith water, NaHCOs solution (10%), Water and dried over Na'zSO4.l 'After ltration, the ether is removed-,through a column leaving a residue of 123 g.'of fairly pure keto ester. The second run is treated similarly and gives g. of fairly pure keto ester. Fifteen grams of the keto ester are made into the Cu salt. This salt is recrystallized four times from benzene and digested with alco hol. vA sample is submitted for analysis.v t

Anal.-Calcd. for CuCazHzsOsSz: C, 56.65;' H', 5.65; Cu, 9.39. Found: C, 56.73; H, 5.97; Cu, 9.56.

This Cu salt is again regenerated into keto ester in the usual manner and submitted for analysis.

AnaZ.-Calcd. for CisH2oO4S;'C, 62.31; H,6.53.

vFound: C, 62.53; H,6.85.

The formula of the keto ester is l C o o 02H5 O Il CH-CHgCHgCHg-O--vCgHi Example ,3.-4-carbethomy-3-keto-2-y-benzyloxypropyltetrahydrothiophene The alcohol is'removed from a solution 01511.35:

g. (0.189 mole) of Isodium in 70 ml. of absolute y alcohol. The dry NaOEt is kept under arl at` 'mosphere of N2 While lumps are brokenup and v"of dry benzene. The whole is shaken thoroughly', jV keeping N2 present at all times. The reactionbe-'" cornes warm so it is cooled in water. The'dark brown solution is allowed to stand overnight at room temperature. To the cooled solution is added 20 ml. of glacial acetic acid dissolved in 160 ml. of water. The layers are separated, the water layer is extracted twice with benzene. The benzene fractions are combined, washed with water, twice with Nal-ICOS solution, and once with saturated NaCl solution, then dried over NazSOi. Benzene is removed through a short column, first by distillation at atmospheric pressure, then at reduced pressure. The residue weighs 26.44 g. and gives a red coloration with FeCla. It formsau sait with Cu Ac 2 solution. The keto esterli's purified through the copper salt by shaking small portions of the ester witha saturated solutionyoff, Cu(Ac)2.H2O in water. The dark greensaltfis. soluble in ether so it is extracted from the water phase withthis solvent. Evaporation of the ethen and addition of petroleum ether and then stirring produce a light green crystalline compound. The product is collected in a Buchner funnel, is washed With Water until free of Cu(Ac)2 and acetic acid, then is dried in a vacuum desiccator over P205. Weight 23.5 g. A portion of the salt is recrystallized several times from 95% alcohol to constant M. P. of '7-108 C. with softening at 105 C.

AML-Calcd. for C34H4408S2C11: C, 57.64; H, 6.26; Cu, 8.97. Found: C, 57.55; H, 6.04; Cu, 9.10. The keto ester is regenerated by shaking the ether solution of the salt with a solution of 5 m1. of H2SO4 in 80 ml. of water. The blue water phase is removed and the ether layer is Washed once with Water, once with 1.0% NaHCOs solution, once with saturated NaCl solution, then dried over Na2SO4 overnight. Removal of the salt and ether leaves 20.4 g. of keto ester, yield 69%. An analysis is made on this compound. Anal.-Calcd. for C1vH22O4S: C, 63.32; H, 6.87, Found: C, 63.41; H, 6,61.

The formula of the keto ester is The examples given above are for purposes of illustrating the invention only. In its broader aspects, the invention is not limited to the specific compounds and conditions givenvin the examples and numerous variations therefrom, which are nevertheless Within the scope of the invention, will occur to those skilled in the art.

The carboalkoxyalkyl a carboalkoxyalkyl suliides used as starting materials for the present invention can be prepared as described in our Patent No. 2,468,426; issued April 26, 1949.

What we claim as our invention is:

1. 4 carboethoxy 3 keto 2 "y phenoxy propyltetrahydrothiophene of formula,

C o o 02H5 O my t 6 2. 4 carboethoxy 3 keto 2 'y benzyl oxypropyltetrahydrothiophene of formula,

C O O 02H5 O (l) CH-CHQCHQCHn-O-CHzCaHn 3. In a process for the preparation of a 4 carboalkoxy 3 keto 2 alkyl tetrahydrothiophene through internal condensation of a carboalkoxyalkyl-a-carboalkoxyalkyl sulfide by means of an alkaline condensing agent, the steps consisting of purifying the 4-carboalkoxy- 3-keto-2alkyl-tetrahydrothiophene by converting it to its copper chelate derivative, crystallizing said chelate derivative from a solvent in order to separate it from impurities soluble in said solvent, and regenerating the said thiophene by treating the crystalline chelate derivative with dilute mineral acid.

4. The steps comprising adding an ether solution of a 4carboalkoXy-S-keto-Z-alkyl-tetrahydrothiophene to an aqueous solution of a copper salt, thereby converting it to its copper chelate derivative, crystallizing said chelate derivative from benzene and regenerating said thiophene with dilute mineral acid.

LEE C. CHENEY. JOHN ROBERT PIENING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,424,007 Moore et al July 15, 1947 OTHER REFERENCES Schmid: Helv. Chim., Acta, v01. 27, 128, (1944). 

1. 4 - CARBOETHOXY - 3 - KETO - 2 - $ - PHENOXY PROPYLTETRAHYDROTHIOPHENE OF FORMULA,
 4. THE STEPS COMPRISING ADDING AN ETHER SOLUTION OF A 4-CARBOALKOXY-3-KETO-2-ALKYL-TETRAHYDROTHIOPHENE TO AN AQUEOUS SOLUTION OF A COPPER SALT THEREBY CONVERTING IT TO ITS COPPER CHELATE DERIVATIVE, CRYSTALLIZING SAID CHELATE DERIVATIVE FROM BENZENE AND REGENERATING SAID THIOPHENE WITH DILUTE MINERAL ACID. 